Determination of ubiquinone-9 and 10 levels in rat tissues and blood by high-performance liquid chromatography with ultraviolet detection

A high-performance liquid chromatographic (HPLC) method is presented for the simultaneous detection of ubiquinone-9 and 10 in rat tissues such as blood, myocardium, and muscle. After liquid-liquid extraction, the ubiquinones are subsequently analyzed by HPLC with ultraviolet (UV) detection at their maximum absorbance (275 nm). Reference calibration curves in ethanol are used to determine tissular levels of ubiquinones. Because a treatment with HMC-CoA reductase inhibitors is expected to decrease the ubiquinone levels, reference calibration curves are performed to ensure that the ratios (ubiquinone/internal standard) observed in such an experiment could be evaluated directly on a calibration curve. The assay is sensitive (0.0625 μg/mL), reproducible (4% coefficient of variation for ubiquinone-9 and 6% for ubiquinone-10), and linear up to 20 μg/mL (or 100 mg of tissue) for ubiquinone-9 and up to 10 μg/mL (or 100 mg of tissue) for ubiquinone-10. The ubiquinone levels in control tissues or blood are within the ranges of those previously reported.